Educational inequalities associated with health-related behaviours in the adult population of Singapore

INTRODUCTION

Socioeconomic differences in health-related behaviours have been widely studied in the Western populations, but are seldom considered in Asian populations. We examined the effect of education attainment on health-related behaviours (physical activity, cigarette smoking and alcohol consumption) among non-institutionalised Singaporeans aged 18-69 years.

METHODS

We used data from the Singapore National Health Survey 2004. Information on physical activity, cigarette smoking, alcohol consumption and sociodemographic characteristics was collected from 4,084 adults. Age-adjusted prevalence of the three health-related behaviours by educational attainment was calculated by the direct method. Logistic regression models, adjusted for age, gender, ethnic group and employment status, were used to estimate the odds ratio and 95% confidence interval, in order to study the prevalence of health-related behaviours according to educational attainment.

RESULTS

The prevalence of physical inactivity, daily smoking and regular alcohol consumption was found to be consistently highest among men and women with the least education. Prevalence of physical inactivity and smoking was inversely related to educational attainment for both genders. However, no clear gradient was found between education and alcohol consumption for men and women.

CONCLUSION

Less-educated Singaporeans were more likely to smoke daily, drink alcohol regularly or not to exercise regularly. Health promotion policies or programmes aimed at encouraging healthy lifestyles in the Singapore population should take into account the educational inequalities in these health-related behaviours.

Changes in the levels of major cardiovascular risk factors in the multi-ethnic population in Singapore after 12 years of a national non-communicable disease intervention programme

INTRODUCTION

The National Healthy Lifestyle Programme, a population-wide non-communicable disease intervention programme, was started in 1992. A National Health Survey is carried out every six years to evaluate the impact of this programme on the cardiovascular risk factor profile of the resident population of Singapore.

METHODS

The 2004 National Health Survey (NHS 04) was a population-based survey carried out over a period of four months from September to December 2004. A combination of disproportionate stratified sampling and systematic sampling was used to select a representative sample (n=7,078) for the survey. The reference population comprised 2.4 million multi-racial Singaporeans aged 18-69 years. Anthropometric and blood pressure measurements were carried out on all subjects and blood samples were taken for biochemical analysis. The results were compared with those of a similar survey conducted in 1998.

RESULTS

A total of 4,084 Singapore residents took part in the survey, giving a response rate of 57.7 percent. The age-standardised prevalence of hypertension (greater than or equal to 140/90 mmHg) in Singapore residents aged 30-69 years decreased from 28.0 percent in 1998 to 24.0 percent (p-value is less than 0.001) in 2004. The prevalence of high total cholesterol (greater than or equal to 6.2 mmol/L) among those aged 18-69 years fell from 26.0 percent in 1998 to 18.1 percent (p-value is less than 0.001) in 2004. The prevalence of diabetes mellitus in residents aged 18-69 years in 2004 was 7.8 percent, compared to the 1998 level of 9.5 percent (p-value is less than 0.01). The level of obesity (body mass index is greater than or equal to 30 kg/sqm) increased slightly from 6.2 percent in 1998 to 6.8 percent (p-value equals 0.1627). The prevalence of daily smoking decreased from 15.0 percent in 1998 to 12.5 percent in 2004 (p-value is less than 0.001), while that of regular exercise increased from 17.0 percent to 25.0 percent (p-value is less than 0.001). Ethnic differences in the prevalence of diabetes mellitus, hypertension, hypercholesterolaemia, and exercise were observed.

CONCLUSION

The NHS 04 results suggest that the National Healthy Lifestyle Programme significantly decreased daily smoking, high blood cholesterol and hypertension, and increased regular exercise over 1998 levels. The results also suggest that the programme stabilised the prevalence of obesity and diabetes mellitus.

Group IIA secretory phospholipase A2 stimulates exocytosis and neurotransmitter release in pheochromocytoma-12 cells and cultured rat hippocampal neurons

Recent evidence shows that secretory phospholipase A2 (sPLA2) may play a role in membrane fusion and fission, and may thus affect neurotransmission. The present study therefore aimed to elucidate the effects of sPLA2 on vesicle exocytosis. External application of group IIA sPLA2 (purified crotoxin subunit B or purified human synovial sPLA2) caused an immediate increase in exocytosis and neurotransmitter release in pheochromocytoma-12 (PC12) cells, detected by carbon fiber electrodes placed near the cells, or by changes in membrane capacitance of the cells. EGTA and a specific inhibitor of sPLA2 activity, 12-epi-scalaradial, abolished the increase in neurotransmitter release, indicating that the effect of sPLA2 was dependent on calcium and sPLA2 enzymatic activity. A similar increase in neurotransmitter release was also observed in hippocampal neurons after external application of sPLA2, as detected by changes in membrane capacitance of the neurons. In contrast to external application, internal application of sPLA2 to PC12 cells and neurons produced blockade of neurotransmitter release. Our recent studies showed high levels of sPLA2 activity in the normal rat hippocampus, medulla oblongata and cerebral neocortex. The sPLA2 activity in the hippocampus was significantly increased, after kainate-induced neuronal injury. The observed effects of sPLA2 on neurotransmitter release in this study may therefore have a physiological, as well as a pathological role.

Seroprevalence of IgG antibodies against Chlamydia pneumoniae in Chinese, Malays and Asian Indians in Singapore

BACKGROUND

Chlamydia pneumoniae, a bacterium that causes respiratory infections, is probably under-diagnosed. There is also interest in its possible role in the aetiology of coronary heart disease. This is the first population-based seroprevalence survey of C. pneumoniae infection in Singapore.

METHODS

A random sample of 1,068 people aged 18-69 years was selected from the participants of the Singapore National Health Survey conducted in 1998. Sera and data on certain clinical measurements and conditions had been collected. IgG antibodies for C. pneumoniae were detected using an indirect microimmunofluorescence test and positivity graded. Seropositivity was defined as IgG titre >/=1:16.

RESULTS

There were no statistically significant differences in the prevalence rates of seropositivity to C. pneumoniae for age group 18-69 years among the three ethnic groups, i.e. Chinese (males 76.7%, females 68.3%), Malays (males 75.4%, females 59.1%), and Asian Indians (males 74.6%, females 59.4%). The seropositivity rate for people aged 18-69 years in Singapore was 75.0% for males and 65.5% for females (difference of 9.5%, P < 0.001). In both genders combined, seropositivity increased from 46.5% in the age group 18-29 to reach a plateau of 78.9% in the age group 40-49, which remained stable to 60-69 years. There was no association of seropositivity with smoking, diabetes mellitus, hypertension or body mass index after adjustment for age and gender.

CONCLUSION

The high prevalence rates in our study population and the higher rate in males compared to females are consistent with studies from other parts of the world. No significant difference in prevalence rates was observed among Chinese, Malays and Indians. The pattern of rising and levelling off of seropositivity with age suggests that C. pneumoniae infection occurs early in life, and in older ages the high level of seropositivity is probably maintained by re-infections or chronic infections. Chlamydia pneumoniae infection was not found to be associated with the cardiovascular risk factors examined.

Hepatitis B Seroprevalence Study 1999

Hepatitis B is a disease of public health importance in Singapore. A study was conducted in 1999 to estimate the overall and gender-, age- and ethnic-specific prevalence of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and antibody to hepatitis B surface antigen in the Singapore population. A cross-sectional sample of the Singapore population constituting 4,698 Singapore residents aged 18-69 years was surveyed. This was the first time a large-scale study has been conducted to assess the hepatitis B seroprevalence rates in the Singapore population. The overall prevalence of the HBsAg in the general population was estimated to be about 4%. About 13% of the HBsAg carriers were also HBeAg positive. Only about 40% of the population had immunity to hepatitis B virus either through immunisation or from previous exposure to the virus. There was still a large proportion (60%) of the population who had no immunity, especially the younger age group of 18-29 years where only 28% had immunity. There is a need to strengthen the hepatitis B immunisation programme to reach out to those who have no immunity, especially the young adults.

Multiple phosphorylation sites in RGS16 differentially modulate its GAP activity

Regulators of G-protein signaling (RGS) are GTPase-activating proteins (GAP) for activated Galpha subunits. We found that mouse RGS16, when expressed in HEK293T cells, is phosphorylated constitutively at serine 194 based on in vivo orthophosphate labeling experiments, while serine 53 is phosphorylated in a ligand-dependent manner upon stimulation by epinephrine in cells expressing the alpha2A adrenergic receptor. Phosphorylation on both sites impairs its GAP activity and subsequent attenuation on heterotrimeric G-protein-stimulated extracellular signal-regulated protein kinase activity. This is the first report of RGS functional downregulation by phosphorylation via a G-protein-coupled receptor.

Specific induction of RGS16 (regulator of G-protein signalling 16) mRNA by protein kinase C in CEM leukaemia cells is mediated via tumour necrosis factor alpha in a calcium-sensitive manner

The RGS (regulator of G-protein signalling) proteins are GTPase-activating proteins for activated Galpha subunits. We investigated the effects of protein kinase C (PKC) on RGS proteins in various T cell lines by treating them with PMA. mRNA levels of both RGS16 and tumour necrosis factor alpha (TNFalpha) were found to be up-regulated in CEM leukaemia cells in a PKC-dependent manner. Mezerein, a non-phorbol-ester activator of PKC, also elevated RGS16 and TNFalpha mRNA levels, while the specific PKC inhibitor Go6983 abrogated their expression. In view of the slower kinetics of PMA-induced RGS16 expression and the tight correlation between TNFalpha and RGS16 mRNA induction among the cell lines studied, we suggest that activation of PKC up-regulates RGS16 via TNFalpha. Indeed, addition of recombinant TNFalpha to CEM cells rapidly stimulated RGS16 mRNA expression independently of PKC. Furthermore, mobilization of calcium by A23187 and thapsigargin blocked the TNFalpha-mediated induction of RGS16, which was reversed by EGTA and by the immunosuppressants FK506 and cyclosporin A, suggesting that the calcineurin/NF-AT (nuclear factor of activated T cells) pathway may repress the up-regulation process. Our results demonstrate for the first time that activation of PKC induces RGS16 expression via TNFalpha in a calcium-sensitive manner, thereby implicating RGS16 in the regulation of T cell responses to inflammation.

Analysis of agonist function at fusion proteins between the IP prostanoid receptor and cognate, unnatural and chimaeric G-proteins

Direct measures of G-protein activation based on guanine nucleotide exchange and hydrolysis are frequently impossible to monitor for receptors which interact predominantly with G(s)alpha. An isolated FLAG (Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys)-epitope-tagged human IP prostanoid receptor and fusion proteins generated between this form of the receptor and the alpha subunits of its cognate G-protein G(s), G(i1), a G-protein which it fails to activate in co-expression studies, and a chimaeric G(i1)-G(s)6 (a form of G(i1) in which the C-terminal six amino acids were replaced with the equivalent sequence of G(s)) were stably expressed in HEK293 cells. These were detected by [(3)H]ligand-binding studies and by immunoblotting with both an anti-FLAG antibody and with appropriate antisera to the G-proteins. Each construct displayed similar affinity to bind the agonist iloprost. Iloprost stimulated adenylate cyclase activity in clones expressing both IP prostanoid receptor and the IP prostanoid receptor-G(s)alpha fusion protein, and both constructs were shown to interact with and activate endogenously expressed G(s)alpha. Addition of iloprost to membranes of cells expressing the isolated receptor resulted in a small stimulation of high-affinity GTPase activity. Iloprost produced no stimulation of GTPase activity which could be attributed to the IP prostanoid receptor-G(i1)alpha fusion. However, the fusion proteins containing either G(s)alpha or G(i1)-G(s)6alpha produced substantially greater stimulation of GTPase activity than the isolated IP prostanoid receptor. Treatment of cells expressing the IP prostanoid receptor-G(i1)-G(s)6alpha fusion protein with a combination of cholera and pertussis toxins allowed direct measurement of agonist activation of the receptor-linked G-protein. Normalization of such results for levels of expression of the IP prostanoid receptor constructs demonstrated a 5-fold higher stimulation of GTPase activity when using the G(s)alpha-containing fusion protein and a 9-fold improvement when using the fusion protein containing G(i1)-G(s)6alpha to detect G-protein activation compared with expression of the isolated receptor.

Selective activation of a chimeric Gi1/Gs G protein alpha subunit by the human IP prostanoid receptor: analysis using agonist stimulation of high affinity GTPase activity and [35S]guanosine-5'-O-(3-thio)triphosphate binding

A FLAG-tagged form of the human IP prostanoid receptor was expressed stably in HEK 293 cells. This bound [3H]iloprost with high affinity and stimulated cAMP production when exposed to agonist. Iloprost produced weak stimulation of GTPase activity and [35S]guanosine-5'-O-(3-thio)triphosphate binding in membranes of these cells. Pretreatment of cells with pertussis toxin did not modify iloprost-mediated stimulation, but this was blocked by cholera toxin. The effects of iloprost were not increased by coexpression of either Gsalpha or Gi1alpha. In contrast, coexpression of a chimeric G protein alpha subunit in which the carboxyl-terminal six amino acids of Gi1alpha were altered to those of Gsalpha resulted in robust stimulation by iloprost. Because the chimeric G protein alpha subunit (Gi1/Gs6alpha) is not a substrate for either pertussis or cholera toxin, pretreatment of cells coexpressing the IP prostanoid receptor and Gi1/Gs6alpha with a mixture of these toxins resulted in resolution of the signal derived from activation of the chimeric G protein. Agonist-stimulated [35S]guanosine-5'-O-(3-thio)triphosphate binding and GTPase activity assays are the most commonly used strategies to examine interactions between G protein-coupled receptors and G proteins. These usually are not appropriate for receptors such as the IP prostanoid receptor that interact with G proteins with low rates of guanine nucleotide exchange and hydrolysis. Chimeric G proteins such as Gi1/Gs6alpha that allow appropriate receptor contacts to be converted to the higher nucleotide turnover rates typical of the Gi family G proteins can overcome this and offer a novel means to examine agonist function at such receptors.

Characterization of protein complexes formed on the repressor elements of the human tumor necrosis factor alpha gene

Human tumor necrosis factor alpha (TNF-alpha) is an important cytokine responsible for pleiotropic effects in vivo. The expression of TNF-alpha is under both positive and negative regulation. Previously we showed that a 108 bp region (-280 to -172) in the TNF-alpha promoter represses TNF-alpha transcription in U937 cells. We also demonstrated that a smaller region of the promoter spanning base pairs -254 and -230 is sufficient for repressor function. This 25 bp TNF-alpha repressor site (TRS) contains a 10 bp sequence homologous to the binding site of activator protein AP-2, yet it does not bind the AP-2 protein. In this study, we demonstrate that this 10 bp core sequence is an essential element for the repressor function of the TRS. Using gel retardation analysis with the 108 bp repressor element and the TRS as probes, multiple specific DNA binding complexes have been identified from U937 nuclear extracts. The complexes B, C, and D on the 108 bp probe and the three major complexes on the 25 bp TRS probe are also present in Jurkat and Mono Mac 6 cells, and their abundance in these cell lines seems to correlate with their postulated repressor function. We have demonstrated that the major TRS binding proteins, with estimated MWs of 30-60 kD, copurify on a heparin agarose column and on a DNA affinity column conjugated with the 10 bp core sequence.

The effect of side chain conformation on the carbon-13 substituent chemical shifts of N-substituted benzamides

The carbon-13 substituent chemical shifts of the ipso and carbonyl atoms in the para-substituted series Z-C6H4CONY2 (where Y = Me, Pri, Ph) have been measured at low dilution in (D)chloroform, and dimethyl sulfoxide. The DSP equation has been shown to hold for varying side chain conformations with high precision when the same resonance substituent parameter is used. Analysis of these data by the DSP equation indicates that the 'reverse substituent chemical shift effect' for the carbonyl atom is substantially due to a localized polarization of the π-electron system of the amide side chain. The ratio of localized to extended π-polarization of the β position of the amide side chain has been estimated. It is suggested that the effective dielectric constant term for the transmission of field effects by the cavity model varies with side chain conformation. The Cl substituent shifts have been discussed in terms of the shift-charge ratio. A variable-temperature study of the DSP parameters indicates an insignificant temperature effect provided rotation around the benzene ring to amide side chain bond is rapid.

The effect of ring size in N-benzoyl saturated heterocyclic amides

The structures of the N-benzoyl derivatives of aziridine, azetidine, pyrrolidine, piperidine, hexamethyleneimine and heptamethyleneimine in solution have been investigated by 13C n.m.r. spectroscopy. In conjunction with literature crystal structure and dynamic intramolecular exchange data, it has been concluded that N-benzoylaziridine and N-benzoylazetidine possess pyrimidal nitrogen atoms in solution. The N-benzoyl derivatives of pyrrolidine, �piperidine, hexamethyleneimine and heptamethyleneimine have planar or near planar nitrogen atoms.

Torsional angles in N-substituted benzamides and related compounds by carbon-13 N.M.R. chemical shifts

The torsional angles in 30 N-substituted benzamides and related compounds have been estimated by the use of the 13C substituent chemical shifts of the meta and para carbon atoms. Steric interaction between the N-substituted groups and the ortho hydrogen atoms of the benzene ring is the major determinant of non-planarity in these systems. A linear relationship between steric substituent constants of the N-substituted groups of some benzamides and the torsional angles is proposed. Dynamic processes involving rotation about the C-N bond, nitrogen inversion and ring inversion contribute a dynamic steric effect to the overall steric interaction. The preferred conformations of some N-substituted groups is also discussed.

The interaction of dimethyl sulfoxide with N-benzoyl amino acids

The interaction of dimethyl sulfoxide with N-benzoyl amino acids in deuterochloroform has been investigated by 13C n.m.r. spectroscopy. Examination of the chemical shifts of the benzene ring reveals that intermolecular hydrogen bonding between dimethyl sulfoxide and the amido-hydrogen atom increase the effective steric size of the amino hydrogen, resulting in an increase in the torsional angle between the benzene ring and the C(O)NHCH(R)COOH side chain. Self-association of N- benzoyl amino acids in deuterochloroform occurs largely through two COOH...O=C hydrogen bonds and does not involve intermolecular hydrogen bonding to the N-H proton.

Electronic effects of halogen-substituted methyl groups

The electronic effects of the halogen-substituted methyl groups, CHnX3-n, where X is F, Cl, Br or I, have been examined by 13C n.m.r, spectroscopy in a series of α-halogen-substituted toluenes. The substituent chemical shifts of all carbon atoms, as well as the σI and σR0 substituent parameters derived from a dual substituent parameter (DSP) analysis, are examined in terms of hyperconjugative and π-inductive substituent effects. Bulky CHnX3-n substituents cause molecular deformations of the benzene ring, consequently invalidating the derivation of substituent parameters from a DSP analysis.

Torsional angles and substituent effects in phenyl-substituted azoles by carbon-13 N.M.R. chemical shifts

The torsional angles in 31 N-phenyl-substituted azole derivatives have been estimated by use of the 13C substituent chemical shifts of the meta and para carbon atoms. Steric interaction between the C 5 substituent on the azole rings and the ortho hydrogen atoms of the benzene ring is the major cause of non-planarity in these compounds. The azole rings undergo structural deformation with varying substituents on the azole ring. The inductive effect of a number of azole and azolium rings is discussed.

Intramolecular hydrogen bonding in ortho-substituted N,N-dimethylbenzamides

Intramolecular hydrogen bonding in o-hydroxy-, o-amino- and o-mercapto- N,N-dimethylbenzamide has been examined with the help of 1H, 13C n.m.r. and infrared spectroscopy, a study of barriers to rotation about the C- N bond, and a study of substituent effects using a multi-substituent parameter equation. The cyclic intramolecular hydrogen-bonded structure for the o-mercapto compound is non-planar, and conformational isomers have been detected. The order of relative energies of the hydrogen bonds formed in o-substituted N,N-dimethylbenzamides is OH > NH2 > SH, as determined from a rotational barrier probe. It has beenverified that intramolecular hydrogen bonding causes a downfield shift of the 13C n.m.r. chemical shift of the carbonyl group in these compounds.

An evaluation of ultraviolet radiation personnel hazards from selected 400-watt high intensity discharge lamps

A study of selected mercury and multi-vapor lamps, commonly used for working environment illumination, was underta ken to evaluate the scope of the ultraviolet personnel hazards one may expect under various operating conditions of the lamps. Spectral irradiance measurements were made for operating conditions with and without reflector-type luminaires, glass covers on luminaries and outer glass bulbs on the lamps.

Carbon-13 N.M.R. chemical shifts and rotational barriers of ortho-substituted N,N-dimethylbenzamides

The barriers to rotation about the carbon-nitrogen bond and the carbon- 13 N.M.R. chemical shifts of a series of 2-substituted N,N- dimethylbenzamides have been measured. The substituent effects have been examined by a multi-substituent parameter method incorporating a steric effect parameter. The barriers to rotation are subject to a large steric effect, whilst the carbon-13 chemical shifts of the carbonyl group and the methyl groups are dominated by the resonance effect.

Carbon-13 N.M.R. chemical shifts and rotational barriers of para-substituted N,N-dimethylbenzamides

The carbon-13 N.M.R. chemical shifts for a series of para-substituted N,N-dimethylbenzamides have been measured. The substituent induced 13C shifts have been examined by a dual substituent parameter (DSP) method using Hammett-type constants. The barriers to rotation have also been correlated with Hammett-type constants by the DSP method and related to 13C substituent induced shifts. Substituent effects of the bromomethyl, dibromomethyl and tribromomethyl groups have been examined by using the chemical shift and rotational barrier probes.

An evaluation of fluorescent light sources for use in phototherapy of neonatal jaundice

An evaluation of fluorescent lamps for use in the phototherapy of neonatal jaundice was undertaken by making spectral irradiance measurements of each lamp. Conclusions are drawn on the usefulness of current methods of measuring exposure dose to radiation from the lamps. UV hazards from the lamps are evaluated.